2015华数校招笔试详解

public static void bubbleSort(int[] a)
{
    for(int i=a.length-1;i>0;i--)
    {
        for(int j=0;j<i;j++)
         {
            if(a[j]>a[j+1])
            {
                int temp=a[j];
                a[j]=a[j+1];
                a[j+1]=temp;
            }
        }
    }
}        

    public static void selectSort(int[] a){
        for(int i =0;i<a.length;i++)
        {
            int k = i;
            for(int j =i+1;j<a.length;j++)
            {
                if(a[k]>a[j])
                    k=j;
            }
            if(k!=i){
                int temp = a[i];
                a[i]=a[k];
                a[k]=temp;
            }
        } 
    }

public static void insertSort(int[] a){
        for(int i =1;i<a.length;i++){
            int temp = a[i];
            int j;
            for(j =i-1;j>=0&&temp<a[j];j--)
                    a[j+1]=a[j];
            a[j+1] = temp;
        }
 }

public static void shellSort(int[] a){
        int gap = 0;
        while(gap<=a.length){ //改进版insert排序，增加gap跨区域排序
            gap = gap*3+1;
        }
        while(gap>0){
            for(int i =gap;i<a.length;i+=gap){
                int temp = a[i];
                int j;
                for(j =i-gap;j>=0&&temp<a[j];j-=gap){
                    a[j+gap]=a[j];
                }
                a[j+gap] = temp;
            }
            gap = (gap-1)/3;
        }
}

public static void quickSort(int[] a,int low,int high){
        if(low >=high){
            return;
        }
        int start = low;
        int end = high;
        int temp = a[low];
        while(low<high){
            while(low<high&&a[high]>temp){
                high--;
            }
            a[low] = a[high];
            while(low<high&&a[low]<temp){
                low++;
            }
            a[high]=a[low];
        }
        a[low] = temp;
        quickSort(a,start,low-1);
        quickSort(a,low+1,end);
    }

public static void mergeSort(int[] a,int start,int end){//分治法
        if(start<end){
            int mid = (start+end)/2;
            mergeSort(a,start,mid); //递推排序
            mergeSort(a,mid+1,end);
            merge(a,start,mid,mid+1,end);
        }
    }
    private static void merge(int[] a, int start, int mid, int i, int end) {
        // TODO Auto-generated method stub
        int m = start;
        int temp[] = new int[end-start+1];
        int k = 0;
        while(start<=mid&&i<=end){
            if(a[start]<a[i]){
                temp[k++] = a[start++];
            }else{
                temp[k++] = a[i++];
            }
        }
        while(start<=mid){
            temp[k++] = a[start++];
        }
        while(i<=end){
            temp[k++] = a[i++];
        }
        for(int element:temp){//将排好的数组替换以前的
            a[m++] = element;
        }
    }

public static void heapSort(int[] a){
        createMaxHeap(a);
        for(int i=a.length-1;i>0;i--){
            int temp = a[0];
            a[0]=a[i];
            a[i]=temp;
            maxHeap(a,1,i);
        }
    }
    private static void createMaxHeap(int[] a) {
        // TODO Auto-generated method stub
        int startNode = a.length/2; 
        for(int i = startNode;i>0;i--){
            maxHeap(a,i,a.length);
        }
    }
    private static void maxHeap(int[] a, int startNode, int length) {
        // TODO Auto-generated method stub
        int leftNode = 2*startNode;
        int rightNode = 2*startNode+1;
        int maxNode = startNode;
        if(leftNode<=length&&a[leftNode-1]>a[startNode-1]){//只考虑length以内的家族,数组与节点相差1
            maxNode = leftNode;
        }
        if(rightNode<=length&&a[rightNode-1]>a[maxNode-1]){
            maxNode = rightNode;
        }
        if(maxNode!=startNode){
            int temp = a[maxNode-1];
            a[maxNode-1]=a[startNode-1];
            a[startNode-1]=temp;
            maxHeap(a,maxNode,length);//调整交换后的最大值对其孩子的影响
        }
    }

 try{   
    //加载MySql的驱动类   
    Class.forName("sun.jbdc.odbc.jdbcOdbcDriver") ;   
 }catch(ClassNotFoundException e){   
    System.out.println("找不到驱动程序类 ，加载驱动失败！");   
    e.printStackTrace() ;   
 }    
    //连接MySql数据库，用户名和密码都是root   
 String url = "jdbc:odbc:people" ;    
 String username = "root" ;   
 String password = "root" ;   
 try{   
    Connection con =    
             DriverManager.getConnection(url , username , password ) ;   
 }catch(SQLException se){   
    System.out.println("数据库连接失败！");   
    se.printStackTrace() ;   
}  
Statement stmt = con.createStatement() ;   
ResultSet rs = stmt.executeQuery("SELECT * FROM Staff where ID=‘001‘") ;
while(rs.next()){   
        String name = rs.getString("name") ;   
        String name1 = rs.getString(1) ; // or此方法比较高效 
 }
if(rs != null){   // 关闭记录集   
        try{   
            rs.close() ;   
        }catch(SQLException e){   
            e.printStackTrace() ;   
        }   
}   
if(stmt != null){   // 关闭声明   
        try{   
            stmt.close() ;   
        }catch(SQLException e){   
            e.printStackTrace() ;   
        }   
 }   
if(con != null){  // 关闭连接对象   
         try{   
            con.close() ;   
         }catch(SQLException e){   
            e.printStackTrace() ;   
         }   
}